Laminated glass is a glass sheet in which two or more glass sheets are laminated with a resin film of polyvinyl butyral or the like sandwiched therebetween. Therefore, the laminated glass has characteristics that it is difficult to be perforatedly broken, and that even if it is damaged, it may keep its original shape while cracked but not scattered in pieces. Accordingly, the laminated glass is widely used as window glass of an automobile, window glass of a railroad car, a windshield of an aircraft, a porthole, glass for a water tank, window glass of a building, security glass and the like.
Some of producing methods for laminated glass include a process for pre-pressing two or more glass sheets with a resin film sandwiched therebetween. In the process for pre-pressing, for example, an unbonded body including two or more glass sheets laminated with a resin film sandwiched therebetween is placed in a bag (a bag member) for use in producing of laminated glass. Next, air remaining in the bag member is evacuated, so as to press the unbonded body with the bag member. Subsequently, the unbonded body closely adhered by pressurizing may be heated while keeping the pressure so as to perform the pre-pressing. A holding tool for the pre-pressing used in such a production method for laminated glass is required to apply a pressure evenly to the whole surface of the glass sheets with the atmospheric pressure by evacuating air from the bag member. Therefore, it may be made of a laminated cloth in which a rubber or synthetic resin film with flexibility and airtightness is laminated on both faces of a base cloth. Alternatively, a film used in the bag member may be further provided with stretching properties as far as it is a material having flexibility and airtightness. In this case, when the stretching properties are limited to a prescribed range, the position for holding the unbonded body may be preferably stabilized.
Patent Document 1 mentioned below discloses an exemplary case in which an unbonded body including two or more glass sheets laminated with a resin film sandwiched therebetween is placed in a heating/pressing bag for use in producing of laminated glass and the heating/pressing bag for use in producing of laminated glass is attached to two pairs of endless track rotating along a horizontal plane in the pre-pressing process. The structure of the heating/pressing bag for use in producing of laminated glass disclosed in Patent Document 1 is illustrated in FIG. 11. The bag 17 of FIG. 11 is in a substantially square shape, has an opening on one side 14 and is closed on the other side 15 and upper and lower sides 12 and 13. The bag 17 is suspended down from a rail 18 with a plurality of suspending tools 19. The plural suspending tools 19 are a plurality of springs for attaching the upper side 12 alone out of the four sides of the bag 17 to the rail 18. On the other hand, the bag 17 has evacuating ports 16 for evacuating the bag 17 in the vicinity of the ends of the lower side 13 disposed in a lower position when suspended. The opening of the bag 17 is disposed on a right/left side of the suspending bag 17, namely, on the side 14, and is closed/opened with shape retention rods 10a and 10b. A shape retention rod 10c is adhered to the other closed side 15, and the upper end of the shape retention rod 10c is fit in the rail 18.